Chow Phillip E, Chu Fang-I, Agazaryan Nzhde, Cao Minsong, Tyran Margeurite, Yang Yingli, Low Daniel, Raldow Ann, Lee Percy, Steinberg Michael, Lamb James M
David Geffen School of Medicine at the University of California, Los Angeles, California.
Institut Paoli Calmettes, Centre de lute contre le Cancer, Marseille, France.
Adv Radiat Oncol. 2021 Mar 3;6(3):100682. doi: 10.1016/j.adro.2021.100682. eCollection 2021 May-Jun.
Stereotactic magnetic resonance image-guided adaptive radiation therapy (SMART) is an emerging technique that shows promise in the treatment of pancreatic cancer and other abdominopelvic malignancies. However, it is unknown whether the time-limited nature of on-table adaptive planning may result in dosimetrically suboptimal plans. The purpose of this study was to quantitatively address that question through systemic retrospective replanning of treated on-table adaptive pancreatic cancer cases.
Of 74 consecutive adapted fractions, 30 were retrospectively replanned based on deficiencies in planning target volume (PTV) and gross tumor volume (GTV) coverage or doses to organs-at-risk (OARs) that exceeded ideal constraints. Retrospective plans were created by adjusting dose-volume objectives in an iterative fashion until deemed optimized. The goal of replanning was to improve PTV/GTV coverage while keeping the dose to gastrointestinal OARs the same or lower or to reduce OAR doses while keeping PTV coverage the same or higher. The global maximum dose was required to be maintained within 2% of that of the treated adaptive plan to eliminate it as a confounding factor. A threshold of 5% improvement in PTV coverage or 5% decrease in OAR dose was used to define a clinically significant improvement.
Of the 30 replans, 7 obtained at least 5% PTV coverage improvement. The average increase in PTV coverage for these plans was 11%. No plans were clinically significantly improved in terms of OAR sparing. Changes in beam-on time did not show any correlation. Statistical analysis via a linear mixed-effects model with a nested random effect suggested that both GTV and PTV coverage were improved over SMART process plans by 0.91 cc ( = .02) and 2.03 cc ( < .001), respectively.
Dosimetric plan quality of at least 10% of SMART fractions may be improved through more extensive replanning than is currently performed on-table. Further work is needed to develop an automated replanning workflow to streamline the in-depth replanning process to better fit into an on-table adaptive workflow.
立体定向磁共振图像引导的自适应放射治疗（SMART）是一种新兴技术，在胰腺癌和其他腹盆腔恶性肿瘤的治疗中显示出前景。然而，术中自适应计划的时间限制特性是否会导致剂量学上欠佳的计划尚不清楚。本研究的目的是通过对已治疗的术中自适应胰腺癌病例进行系统性回顾性重新计划来定量解决该问题。
在74个连续的自适应分次中，基于计划靶体积（PTV）和大体肿瘤体积（GTV）覆盖不足或危及器官（OAR）的剂量超过理想限制，对30个进行了回顾性重新计划。回顾性计划通过以迭代方式调整剂量体积目标来创建，直到被认为是优化的。重新计划的目标是在保持胃肠道OAR剂量相同或更低的同时提高PTV/GTV覆盖，或者在保持PTV覆盖相同或更高的同时降低OAR剂量。全局最大剂量需要保持在已治疗的自适应计划的2%以内，以消除其作为混杂因素。PTV覆盖提高5%或OAR剂量降低5%的阈值用于定义临床上显著的改善。
在30个重新计划中, 7个获得了至少5%的PTV覆盖改善。这些计划的PTV覆盖平均增加了11%。在OAR保护方面，没有计划在临床上得到显著改善。照射时间的变化没有显示出任何相关性。通过具有嵌套随机效应的线性混合效应模型进行的统计分析表明，与SMART过程计划相比，GTV和PTV覆盖分别提高了0.91 cc（P = .02）和2.03 cc（P < .001）。
通过比目前术中进行的更广泛的重新计划，至少10%的SMART分次的剂量学计划质量可能得到改善。需要进一步开展工作来开发自动重新计划工作流程，以简化深入的重新计划过程，使其更好地适应术中自适应工作流程。
